So, does that leave any time for creating new awesome themes, or are you going to be stuck updating stuff for the rest of your life?

I wish!!! 
Kinduv sucks, when one of your theme goes platinum (DominantNegative's downloads, on various sites, has well over 30,000 downloads) you'll get nothing but requests for "can I port it to this?" or "are you gonna make it for this?" or "are you gonna add this feature?". It's a good kinduv hurt: you know you're appreciated.
Funny how things can turn out... you want people to enjoy your themes, but once they do, it's a whole different headache.
Maintenance is the current problem. Both for skins and the sites. Rainlendar has come up with updates so fast that it's literally gone through probably about 30-40 minor and major updates since I made most of my skins for it several years back. Sysmetrix and LiteStep have likewise changed significantly. Sysmetrix has expanded to be just about a complete widget solution in-and-of-itself. I skinned for it before it had probably half the features it's got now.
The time invested in the skinyourscreen.com family of websites has eaten into skinning time. I hope you guys will forgive my apparent absence at times... I'm either busy skinning or focusing on my family and graduate research. The
skins site is still less than 40% complete in my mind... I'm trying to make individual article pages for each and every skin there at the moment, rather than just having a single article with a paragraph on each. This will permit each skin to have its own associated comments.
There have been MANY times where I've debated retreating - killing all the mrbiotech email accounts and just forgetting about my published themes to spend my time in other matters. No more maintenance, no more requests, but no more skinning. As many times as I've tried, it just hasn't happened, though. I'll be sifting through my graphics folder where I'm working on new recipes, techniques, and graphical projects and know with veritable certainty there's no way I can leave it behind.

I get graphical ideas and they have to manifest... it's almost as if I don't work on 'em, polish 'em and publish 'em that my brain will overload and explode. Plus, there are so many fine people I've met through skinning, people I've gotten to know over years. It's a good community, and I know there's no way I can abandon it.
So, for the time being at least, time is really short juggling so many tasks. But, y'know, it's just so fun!
EDIT: - Fixed the borked link. Thanks for the heads-up, Haxer!